Silicone compositions are well known products offering premium properties in a wide variety of applications. For example, certain flexible silicone resin systems have been found useful as electronic conformal and junction coatings which are used for passivating and protecting semiconductor surfaces, and serve to assure optimal electrical performance. Such silicone materials are chosen since they offer rapid cure rates which improve production efficiency. The softness of these materials helps to minimize the vibration and shock experienced by such semiconductor devices and the low viscosity of such silicone coating compositions provides for ease of handling.
Such silicone electronic coatings are useful in a number of applications. A flexible conformal coating of such material can provide mechanical and electrical insulation prior to molding of plastic power transistors, for example. These materials can also be used a a light pipe or lens which insulates and isolates LED's and photocouplers and may be utilized with or without further encapsulation. These silicone junction coating materials are also a resilient coating which can be used directly over transistors, diodes and monolithic integrated circuit chips in order to prevent damage during and after final potting or sealing. Additionally, these coatings can be used as a thin section potting material for extra protection in cavity type packages in order to provide primary mechanical and chemical protection.
Brown in U.S. Pat. No. 4,340,710, incorporated herein by reference, discloses platinum-catalyzed one-package silicone electronic coating materials with good shelf life. Brown's products comprise a major amount of a vinyl functional linear siloxane fluid, an organohydrogenpolysiloxane, a platinum catalyst, and a combination of cure inhibitors comprised of an unsaturated isocyanurate and a dialkylacetylenedicarboxylate. These products are coated on a substrate and cured at temperatures from about 70.degree. C. to 150.degree. C.
Although Brown reports improved adhesion of his materials when compared to materials of the prior art, additional improvement has been found to be desirable, particularly in adhesion to thermoplastic resins such as polyolefins, polycarbonate, polyether, polyamide, polyimide resins, their mixtures, and the like.
It is an object of the invention to provide electronic coating compositions having improved adhesion to substrates.
This and other objects will become apparent to one skilled in the art upon consideration of the present specification and claims.